reviews: Kudos to our Chinese friends for making a great product. I bought this one because I already had a XM-L2 (5000 lumen). I was so impressed with the L2 that I just had to have this one that is 8000 lumen. I have not been disappointed. It is very well made. The head is well designed as a heat sink if you use it on land. It is 11.5 inches long and weight about 3 pounds with batteries. It comes with two sets (4) silicone O rings and 18650 battery adapters (no 18650 batteries included.) You turn it on by turning the blue aluminum ring behind the head. I took it down to 90 feet with no leaks. I would not call this item a flashlight. I call it a small portable sun. I do a lot of night diving and the daylight LEDs give off a beautiful white/bluish light just like the Sun. With this monster it is like turning on a sun underwater. Caveat - you have to tighten the back cap as tight as you can or it wont work, or it will flicker and go out. It also uses a lot of battery power. I turn it off for about 10 seconds every 15 minutes of use. WARNING - do not load the batteries until ready to use. With the much smaller L2 I loaded the batteries before leaving home. I put a heavy piece of duck tape on the slider switch to keep it from turning on. When I opened my bag about 2 hours later, the flashlight had been jarred on and it had melted the silicone on my mask. So, please be careful. This model is much more powerful. I paid $58 for it. A comparable diving flashlight in the US costs several hundred dollars. I would not use this monster for an extended period of time out of the water.